"Horseshoe Crab" I think that they are called, saw them on a TV show about both them and another living fossil the Chambered
Nautilus. From memory a dish was prepared from one which was not particularly
appetizing and involved the creature's eggs which are contained in the
horseshoe shape around the head. Closest thing to a Trilobite which once was
the dominant species in the oceans millions of years ago. Apparently their blue
blood is used for testing of biological contamination in laboratories due to
some unique properties which have enabled the species to survive the millennia
without getting diseased by bacteria and pathogens.